The present invention relates generally to communications and more particularly to methods for rate shifting to improve network performance and implementations of the aforesaid methods.
Data rate shifting is a common mechanism to ensure a reliable wireless link. There are many ways that a wireless link can become degraded (e.g., noise, multipath, fading, interference, etc.). As the link is degraded it becomes increasingly difficult to operate the link at higher data rates because corrupted packets and the subsequent retries consume much of the available bandwidth. A reduction in the data rate is often effective in restoring the quality of the link since the lower data rates can accommodate greater corruptions to the link.
Rate-shifting can be based on the number of packet retries. As the number of packet retries increases, or reaches a certain threshold, the data rate can be reduced. However, a problem with this technique is that packet loss due to collisions are interpreted the same as packet loss due to a poor channel, interference, or large amounts of noise. Packet collisions within the network under normal operation with large numbers of clients and heavy traffic load can also cause packets to become corrupted. If the packet loss is due to collisions, then rate shifting to a reduced data rate is not effective and may severely reduce network performance since lower data rates increase a packet's transmission time and therefore its collision probability.